Currently there are a large variety of commercially available light-sensitive materials and image-forming methods to be used therewith. Of those light-sensitive materials, the materials used in markets where large numbers of finished prints are required in a short period of time, silver bromide or silver chloride emulsions containing substantially no silver iodide have been used.
In recent years, requirements for improvements in rapid processing performance for color photographic paper have been increasing thereby increasing the amount of research associated with those requirements. It is known that an increase in the amount of silver chloride content in a silver halide emulsion results in a marked improvement in developing speed, and there has been a movement in the market to convert to the use of higher silver chloride content emulsions for color photographic paper. However, silver halide emulsions having high silver chloride content have drawbacks in that it is difficult to obtain a high sensitivity and a hard gradation with conventional chemical sensitization.
There have been several attempts to provide high silver chloride emulsions with high sensitivity. For example, a technique is disclosed in JP-A-64-26837 (the term "JP-A" as used herewith means an unexamined published Japanese patent application), where a silver bromide rich phase is formed in the vicinity of an apex of a silver halide host grain to achieve a high sensitivity. Methods for forming a silver bromide rich phase in the vicinity of an apex of a silver halide host grain include, for example, the method in which a water soluble bromine compound is added to a silver halide host grain described in JP-A-62-7040; a method in which silver halide grains having smaller average grain sizes and larger silver bromide contents than those of silver halide host grains, are added to the silver halide host grains to form a silver bromide rich phase is described in JP-A-64-26840; and a method in which bromine or a bromine controlled release agent is added is described in JP-A-1-285942. However, a "clearance", e.g., a photograph with a sharp image taken even in a bright landscape, in a highlight portion is inferior with such materials compared with those using a high silver bromide emulsion.